This timely volume provides a second collection of Thomas Humphrey's papers in the area of the history of economic thought and is a long-awaited companion to his critically acclaimed first volume of essays Money, Banking and Inflation. Unlike the first volume, this book does not focus specifically on traditional central bank concerns but addresses key concepts, theories and tools in the area of money, exchange and production which have proved indispensable to the development of economics. Each essay focuses on a prominent theory or tool, examines its essential elements, identifies its origins and traces its development across a succession of economists, problems, controversies and applications. In this way, the book shows how the history of economic thought can be illustrated through the development of tools and concepts rather than through schools of thought and prominent individuals. This outstanding collection will be invaluable to historians of economic thought as well as to students and scholars of methodology, philosophy and monetary and financial economics.